The holidays mean travel, and travel means memories — and the photos that capture them. How can you spare your phone an overload and keep your images safe at the same time? Put them in the Cloud. Dropbox's Carousel and Amazon's Cloud Drive Photos can help.

Revised to more accurately Dropbox/Carousel pricing plans.

Over the extended Thanksgiving weekend, we Americans will take something more than a billion digital photos. We'll capture video snippets in the hundreds of thousands. We'll use our smartphones for most of this, and the more recent our phones are, the better those photos will be — and the bigger. 5 megapixels; 8 megapixels; 720 or 1080p — by the time we board the return flight, our overstuffed devices will struggle to find room for so much as a song. Which memories will we forego for lack of space? What'll be lost if those phones are damaged, or misplaced?

So why not sidestep physical storage and park your photos in the Cloud? The options, and the mechanics, can be daunting — just ask JLaw, Kate Upton, Kirsten Dunst or the other celebs who gave unwitting demonstrations this summer.

Hacking aside, the choices are numerous. Both Android and iOS offer proprietary solutions. Google, in addition to their charmless Android photo library, offers an awkward form of cloud sync through Google Drive, or a more elegant version through Google+.(Really. It may be the best part of Google+.) There's Box; there's Microsoft's OneDrive; there's Flickr. Some are better than others. But none quite measures up to Dropbox's Carousel or Amazon's Cloud Drive Photos.

First, the criteria.

Speed Mobile bandwidth is precious. Connections waver or drop. Any app negotiating files as big as today's photos needs to wring the most from every transferred byte, and fail gracefully when paths are thin.

Reliability If data security is a goal, dependability can't be a luxury. Are our photos uploaded, or aren't they? Do we have to intervene? Peace of mind is the point.

Background updating Your phone is your camera, but it's also your address book, your browser, your email client, your gossip line, and your library. And, of course, your phone. It's next to impossible to lock up such a device for any length of time. A great storage app should do its lifting in the background, keeping our shots safe while we go about our business (including the business of making more shots).

Cross platform iOS is great. Android is great. The devices come fast and furious these days; a platform's cost-benefit matrix can change from week to week. With all the available options, households — to say nothing of wider social circles — are increasingly ecosystem-diverse. It makes sense to choose a service that's available anywhere and plays well with everything. You don't want your photos in platform jail.

Features Best to focus on the essentials here. Reasonable people can disagree, but I look for the basics of upload, download, broadcast and organization — the app needs to do them all well. Editing is a bonus; there are plenty of good editing apps out there. It’d be hard to prise me from my favorite, especially if the featureset feels second rate or bolted on.

Carousel

Dropbox launched Carousel early this year to paint a friendly face on their core service. And while Dropbox itself is all about utility, Carousel aims at the heart, strumming the languid chords of memory like Don Draper in the brilliant Kodak pitch that might have inspired the app's name. Plucking from Facebook's timeline, distilling Apple's overwrought albums, Carousel blends them with the notion of a photo wall. The result is a stream of images — your life — atop the thin ribbon of time.

Carousel arranges your photos in a "photo wall," with varying sizes to avoid monotony. You can navigate quickly with the timeline along the bottom of your screen.

Carousel's strengths are beauty and simplicity: just your photos, in reverse chronological order. The timeline is a small but potent wheel of captured moments; it seems to spin instead of scroll. Tap a photo to zoom in. Tap again to zoom back out. From the zoomed-in view, interactions are mostly intuitive. Carousel supports the usual kinds of sharing, including, in the iOS version, opening photos in other apps. For a delightful Easter egg, go to "Today" on the timeline and pull up. You'll launch the "Take Me Somewhere" feature, which drops you unpredictably, serendipitously into the river of memory.

Conversation piece

Carousel lets you create direct connections with other Carousel users. It calls these "Conversations." The difference between Carousel conversations and text messages isn't readily apparent; the one perceptible difference is speed. Sharing a photo by text message means waiting while your photo uploads. Carousel's conversation transfers, on the other hand, seem instantaneous.

In fact, speed is a Carousel hallmark. Browsing is zippy. Interactions are zippy. Best of all, uploads are zippy. Whether they're happening on WiFi or a cell network, photos are pulled in quickly, no persuasion or coersion. It's a delight to watch the small white circles at the corners of images trace themselves and disappear, signalling completion. Signalling peace of mind.

Reliability is another Carousel strength. Once set up, it needs almost no supervision. Its automatic backup feature finds photos and begins uploading within seconds of your taking them. And it works in the background, with no perceptible impact on your phone's function. That invisible vigilance and follow-through are Carousel's greatest advantage over other apps; nothing I've tried is its equal (though Google+ comes close on this particular front).

Heritage matters

In part, this is lineage. More than any other company, Dropbox, Carousel's parent, set the standards for consumer cloud computing. Be everywhere; be fast; be reliable — no one gets this combination better. More subtly, Dropbox has extended the sharing economy by making everything you store there accessible through portable links, and by integrating those links directly into the OS, never more than a right-click away. Other services — like Google Drive — offer similar features, some in more robust forms. But they're nowhere near as intuitive, and nowhere near as embedded in everyday flow.

So, in keeping with Dropbox's ubiquitous links approach, what appears to be happening in Carousel's conversations is different from what happens in a text message. In the text message, you actually send the photo to your friend — a physical object, so to speak. In Carousel's "conversations," you send only a link and a preview. The image remains in the cloud. The recipient even has the option to save it directly to her Carousel, bypassing the phone entirely. You can get it on the device if you need it, of course; but most of the time you don't. Why waste bandwidth, or space on your device, till you do?

Carousel features an in-app sharing feature called "Conversations," which lets you share photos without incurring the bandwidth or storage costs.

Carousel's approach generally is to keep everything in the cloud, but give the user a great on-phone experience with high-quality previews and fast interactions. It's so successful that, if you use your phone primarily for browsing, email, and photos, Carousel can save you the cost of an upgrade. Buy the cheapest, lowest-memory phone available; keep your photos in Carousel; keep your local memory tidy, and you'll never run out of space. I spent Fourth of July week in Maine with a bottom-shelf, 8Gb Nexus 4, for instance — nowhere near enough storage for basic apps and all the photos I took. But with Carousel, space felt limitless.

The downside. There isn't much. Carousel's free space allocation takes a bit of decoding, but it's generous. If you're not a Dropbox user and sign up from within the app, you'll get a total of 5Gb free space (2Gb for the basic Dropbox account, another 3Gb as a "bonus" for using Carousel). If you’re already a Dropbox user, you’ll get 3Gb of additional space for using Carousel and turning on its automatic uploading function. $9/month gets you a virtually unfillable 1Tb of space — worth it if you use Dropbox for other things, but maybe not if you only want photo storage.

Amazon Cloud Drive Photos

Amazon's quest to embed itself in your life goes way beyond products. They've got film; television; music; even groceries, recently. Last year they got into the cloud storage game. It's familiar territory for them; Amazon Web Services has been driving some of the internet's busiest sites for nearly half a decade. But now they've got something for consumers. They call it Cloud Drive Photos, and they're hoping it'll become your go-to storage location.

They make a compelling case. You’ll get 5Gb of storage space for free, but if you're one of Amazon's more than 20 million Prime customers storage is unlimited. All the photos you want. The unlimited plan doesn’t include videos, a fact that’s both difficult to uncover and irritating in that Vine, Instagram, and other video apps are quickly making short phone videos the new snapshots, memory-preservation-wise. All the same, for a Prime user, Cloud Drive Photos is clearly a great value.

Keeping it simple

How's the app itself, though? Quite good, in fact. The basic interface, like Carousel's, invokes a photo wall: grid of images, reverse chronological order. There's no timeline on the default view, but months and years appear as clickable tiles — tap them to reveal a sidebar that lets you jump from month to month. It's less sensual than Carousel's memory-jogging spool, but just as functional. You zoom in with a tap in the image, as in Carousel; you zoom out with a back button — entirely functional, but a metaphorical lapse that feels less delightful.

Cloud Drive Photo's approach to interactions is, if anything, even simpler than Carousel's. You can do three things: share (all the standard methods; no "conversations"), download, or delete. There's a handy Info button that reveals photo metadata — date & time shot, date & time uploaded, image size, filename, and location (with a map). On the wall view, there's a "Select" mode similar to Carousel's; but the only bulk actions you get here are Save and Delete — weirdly and unfortunately, no Share.

Like Carousel, Cloud Drive Photos keeps your images on Amazon's servers, giving you just a lightweight preview to work with. This keeps the app speedy. I've found it slightly more laggy than Carousel — the photo wall, for instance, occasionally took several seconds to populate — but still impressive.

Organization, sort of

Cloud Drive does offer a couple of additional ways to organize your photos. The first, "Albums," is more puzzling than helpful. I discovered, for example, that I had some albums even though I'd never created them. They seem to derive from whatever device the photo came from. You can't change them, and the only way to make new ones within Cloud Drive is to go to the desktop browser app. In my case at least, their titles tended to refer to apps in which I'd made edits to images — "Flickr," "Instagram" — not a helpful vector of exploration.

More useful, on the other hand, is the "Videos" tab, which hides all but the videos among your uploads. While both apps store videos similarly, only Cloud Drive Photos lets you view them in isolation like this. I've found it handy for both editing and sharing. And for reintroducing me to videos I took months ago, watched once, and forgot — but shouldn't have. It's a different serendipity than that offered by Carousel's "Take Me Somewhere," but no less magical.

The downside. For a non-Prime user, Cloud Drive Photos is a great deal — if you don't shoot much video. And by "not much," I mean really, hardly ever. I'm a very infrequent videographer, for example; yet I've somehow got 9Gb of them in my account. That would put you well over the free 5Gb limit, and Amazon's prices for additional storage are not as low as those of some competitors. Space on Google Drive, for instance — usable for photos uploaded through the Google+ app — costs less than half what it does on Amazon. Same is true for Dropbox, which has fewer plans but charges less per gigabyte for those it offers.

The Winner?

While you really can't lose with either — and while Amazon Prime subscribers face unlimited temptation — Dropbox's Carousel gets the edge. Better display variety; easier cross-app integration; original features like Conversations, Hiding, and the Take Me Somewhere wheel — it's just more delightful to use. Its class-leading speed and rock-solid reliability also stand out.